DJ Hector Romero, Knuckles' house music peer and fellow Bronx native, posted on Facebook about the loss.

"My heart is heavy at this moment but I know he's in a better place," he wrote.

Questlove, from The Roots, tweeted that Knuckles was underappreciated, and "the dj that djs aspired to be." Actor Idris Elba called him "an innovator."

A photo of Knuckles with (then Sen.) Barack and Michelle Obama in 2004 has been circulating on Twitter. The Obamas were present when a city street, site of the Warehouse, was renamed for Knuckles.

"Over his long career Frankie made his way into the ranks of those artists and innovators who came to this city not just to contribute to a musical genre, but to create one themselves," said Chicago Mayor Rahm Emanuel, in a statement. "In doing so, he also made his way into the hearts of those who knew him and the many more who followed his work."

jesus man. Frankie Knuckles was so under-appreciated. he was the dj that dj's aspired to be. true dance pioneer.